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ICD-10-CM 2027 diagnosis code

A48.1Legionnaires' disease

✓ Billable / specificMCC — major complication/comorbidity

A48.1 is a valid, billable ICD-10-CM code for legionnaires' disease. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Looking up by condition? See ICD-10 code for Legionellosis.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About A48.1

A48.1 is the ICD-10-CM diagnosis code for Legionnaires' disease. It belongs to category A48 (other bacterial diseases, not elsewhere classified), block A30-A49 (other bacterial diseases) and chapter 1 (certain infectious and parasitic diseases). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within A48 (other bacterial diseases, not elsewhere classified), A48.1 is specifically for Legionnaires' disease. Related codes cover gas gangrene (A48.0), Nonpneumonic Legionnaires' disease [Pontiac fever] (A48.2), toxic shock syndrome (A48.3), Brazilian purpuric fever (A48.4), other specified botulism (A48.5) and other specified bacterial diseases (A48.8).

As a secondary diagnosis it is an MCC (major complication or comorbidity), which can move an inpatient stay into the highest-paying "with MCC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 177 (Respiratory Infections and Inflammations with MCC, relative weight 1.6092), DRG 178 (Respiratory Infections and Inflammations with CC, relative weight 0.9744), DRG 179 (Respiratory Infections and Inflammations without CC/MCC, relative weight 0.7345), DRG 791 (Prematurity with Major Problems, relative weight 4.1075), DRG 793 (Full Term Neonate with Major Problems, relative weight 4.2195), DRG 974 (HIV with Major Related Condition with MCC, relative weight 3.0506) and 2 more, in MDC 04 (Diseases and Disorders of the Respiratory System), MDC 15 (Newborns and Other Neonates with Conditions Originating in the Perinatal Period) and MDC 25 (Human Immunodeficiency Virus Infections), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 482.84 (pneumonia due to Legionnaires' disease).

Notes that apply from higher levels

Instructions written at a parent level also apply to A48.1.

› From A48 Other bacterial diseases, not elsewhere classified
Excludes1

Broader instructions also apply from Chapter 1: Certain infectious and parasitic diseases.

Alphabetic index entries

5 entries

Terms in the official ICD-10-CM index that lead to A48.1.

Codes whose notes reference A48.1

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

MDC 15 · Newborns and Other Neonates with Conditions Originating in the Perinatal Period

MDC 15 · Newborns and Other Neonates with Conditions Originating in the Perinatal Period

ICD-9-CM equivalent

Converter →
  • 482.84Pneumonia due to Legionnaires' diseaseexact

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about A48.1

Is A48.1 billable?

Yes. A48.1 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can A48.1 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict A48.1 as a principal diagnosis.

Is A48.1 a CC or MCC?

A48.1 is an MCC (major complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does A48.1 group to?

A48.1 is used in the MS-DRG v44.0 logic for MS-DRG 177 (Respiratory Infections and Inflammations with MCC), MS-DRG 178 (Respiratory Infections and Inflammations with CC), MS-DRG 179 (Respiratory Infections and Inflammations without CC/MCC), MS-DRG 791 (Prematurity with Major Problems), MS-DRG 793 (Full Term Neonate with Major Problems), MS-DRG 974 (HIV with Major Related Condition with MCC) and 2 more. Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for A48.1?

The CMS General Equivalence Mappings map A48.1 to ICD-9-CM 482.84.